Regular expressions are at the heart of pattern-based text-processing. To use regular expressions effectively, one needs to understand them.
Everyone who uses ls is familiar with glob style patterns. Glob rules are useful in many situations, but are too limited for text processing. Regular expressions allow you to describe patterns in finer detail than glob rules.
A typical regular expression to match an e-mail address might look like this:
[a-z0-9_]+@[a-z0-9]+\.[a-z]+.
If this looks weird, don't worry; it is really simple once you understand the concepts through this recipe.
